Thanks for flagging this and filing a radar. Radar has been routed to the right team to fix.

Previously, the Photoshop app icon template used smart objects that were scaled to each of the icon sizes used by the system. With the introduction of the ability to have a single app icon that the system would then scale to any size it needs, having the template structured in this way didn't really make sense. It would have the same end result: A large icon size scaled to smaller sizes. The smaller sizes are there if someone (like you!) wants to make pixel hinted app icon sizes. The masks and app icon grids are meant as a handy reference. But there's no smart object of the largest app icon size. We figured that, in this scenario, putting in a scaled smart object isn't helpful since the vector or raster layers were being tuned for each size. And further, if you're doing this work you probably know how to duplicate and scale layers. As for exporting blank images, the thinking is that developers don't need to add smaller sizes to their asset catalog if they're using the single app icon feature and these smaller icons could just be ignored. But, we set them up to export with Generator for convenience if you choose to make size specific icons. Totally understand that the current structure of the template could be a little confusing. Ultimately something of a judgement call on how to optimize this for the majority of users.